The present invention relates to improvements in a stator winding structure for a gap wwinding type electric rotary machine, in which the stator winding is disposed within a gap defined between the stator core and the rotor core thereof.
In general, the stator winding for a gap winding type electric rotary machine is disposed in a gap between the stator core and the rotor core, and is mounted on the inner surface of the stator core by coil supporting members which project from the inner surface of the stator core in the radial direction. As a result, the stator winding such as provided in the gap winding type electric rotary machine is much more directly influenced by the main magnetic flux of the machine than the stator winding for a slot winding type electric rotary machine in which the stator winding is wound within slots provided on the inner surface of the stator core.
Therefore, in the gap winding type electric rotary machine, fine wires of about 1.0 mm in diameter are usually formed as a strand and bundled together to form one stator conductor. Each stator conductor has a covering insulation over the outer periphery of the stator conductor. Further, a plurality of such stator conductors are gathered and an earth insulation is provided on all of the surfaces to form one stator coil. Every stator coil, or a plurality of such stator coils thus formed, is then mounted on the inner surface of the stator core by means of coil supporting members.
U.S. Pat. No. 3,405,297 to K. D. Madsen shows one example of this kind of stator winding structure, in which the stator winding comprises a plurality of stator coils, each of which is composed of a plurality of conductors respectively surrounded by a suitable insulating material and bundled together to form one stator coil. The stator coil is further solidified by a suitable insulating material surrounding the stator coil and then mounted on the inner surface of the stator core with the assistance of a plurality of coil supporting members projecting from the inner surface of the stator core.
In another embodiment of the prior art, for example, as disclosed in U.S. Pat. No. 3,082,337 to W. D. Horsley, a stator winding comprising a plurality of stator coils is embedded in a detachable cylinder composed of a suitable casting resin, for example, an epoxy-resin, and fixed to the inner surface of the stator core.
However, as described before, the electromagnetic forces generated in the stator coils of a gap winding type electric rotary machine become very large with the aid of the main flux in the air gap. Further, these electromagnetic forces are directly applied to the respective stator coils adjacently disposed in the air gap, which tends to cause various vibration modes in the respective stator coils. The magnitudes, phases and directions of the vibration produced in the respective stator coils are different from each other; therefore, each stator coil oscillates with vibrations different in magnitude, phase and direction from the other stator coils. The electromagnetic forces thus produced with respectively different magnitudes, phase, and directions are exerted on the stator core as individual vibration sources in the electric rotary machine.
Consequently, the stator core suffers from vibrating stresses, local abnormal oscillations and noises. Also, the electrical insulations surrounding the respective stator coils are conspicuously degraded by the vibrating stresses, and local losses and temperature rises are induced in the coils.